Haydn was a prolific composer, as demonstrated in part by his 68 string quartets and 104

symphonies

Explanation:

Franz Joseph Haydn, one of the most important composers of the classical period, died in Vienna on May 31, 1809, at the age of 77. He personified the so-called "Viennese classicism" alongside Wolfgang Amadeus Mozart and Ludwig van Beethoven, forming the so-called "Viennese Trinity". He is considered one of the most important and influential composers in the history of Western classical music with a career that covered from the end of the Baroque to the beginning of Classicism. Having lived most of his life in Austria, Haydn spent almost his entire career as a court musician for the wealthy Eszterházy family. Isolated from other composers, he was, according to himself, "forced to be original". His genius was widely recognized while still alive and was credited with 68 strings and 104 symphonies.